It is generally known and usual to provide axles with twin wheels on heavy-duty utility vehicles, for example on forklift trucks for large ship containers, in order to be able to guarantee extreme loading capacities. In this case it is desirable to arrange the twin wheels to be rotatable relative to one another in order to avoid undesirable slip during turning maneuvers of the vehicle and to avoid severe wear of the tyres of the twin wheels associated with this. U.S. Pat. No. 7,757,795 B2 shows a suitable hub arrangement for this type of twin wheels, in which the wheel hub parts carrying the two twin wheels are rotatably mounted on a (third) intermediate hub part, which on the other hand forms the input of a differential gear driving the wheel hub parts. For this purpose, gear wheels are arranged rotatable on an axially middle portion of the intermediate hub about axles which are perpendicular to the circumference of the intermediate hub part. These gear wheels mesh with toothing rings on the axial ends of the wheel hub parts facing one another, so that the wheel hub parts are only rotatable in directions opposing one another relative to the intermediate hub part. The intermediate hub part is driven via a planetary gear set and braked by means of a wet multiple disc brake. In order to be able to transmit to each wheel hub part a predetermined minimum driving moment or minimum braking moment, slide bearings which are subject to friction are provided in each case between the intermediate hub part and the wheel hub parts, while the differential arrangement additionally operates with friction predetermined by design as well.
All the same, this known hub arrangement is always problematic during braking manoeuvres when the twin wheels, because of road irregularities, are clearly loaded differently and have a correspondingly different traction. The same applies also when the twin wheels roll over road sections with very different friction coefficients. In all these cases it can happen that during a braking manoeuvre the twin wheel with good traction continues to roll largely unbraked while the twin wheel with poor traction slips with direction of rotation opposite to that of the former twin wheel.
A similar arrangement by design and function is the subject of U.S. Pat. No. 2,267,362. In this case, design measures for inhibiting the differential arrangement between the wheel hub parts are provided. In this connection it is utilized that gear wheels of the differential arrangement displace hydraulic lubricants in the differential arrangement in the manner of gear pumps. In this case, increased throttling resistances have to be overcome through design measures according to U.S. Pat. No. 2,267,362 so that the intermediate hub part during driving and braking operation transmits corresponding minimum moments to the wheel hub parts each. All the same, the case may arise under unfavorable conditions that the utilizable braking moments only have the (comparatively low) dimension of the aforementioned minimum moments.
EP 1 288 054 B1 shows the drive of the wheel hub parts of twin wheels via a differential arrangement. In this case, the wheel hub parts are each formed as a hollow wheel of a planetary gear set with planet wheels being rotatably mounted on a stationary planet carrier. The planet wheels each mesh with a sun wheel, which on the other hand is driven via one of the output shafts of the differential arrangement. No measures for transmitting braking forces onto the wheel hub parts are described whatsoever.
EP 1 145 894 B1 shows a twin wheel arrangement, in which the wheel hub parts can be non-positively coupled to one another and only one hub part is directly driven or braked. In this case, it must therefore be always ensured during braking maneuvers on a problematic surface that the wheel hubs are coupled together, which is technically difficult and associated with major construction effort.
EP 1 162 082 B1 on the other hand shows a twin wheel arrangement, the wheel hub parts of which are driven via a differential arrangement. In this case, the differential arrangement is combined with a step-down transmission on the input side in order to be able to transmit high driving moments to the output sides of the differential arrangement if required. No measures whatsoever for enforcing a synchronisation of the wheel hubs are shown.